Alexey, I'm obviously missing something.
If you want to say "Andrew, TCP is safe" then that's cool. I'll just
buzz off and stare unhappily at the SCSI code. But I just need one more
shot at it. :)
kuznet@xxxxxxxxxxxxx wrote:
>
> Even not counting that del_timer_sync is deadlocky,
> it should not be ever used for static timers,
static struct timer_list timer;
int foo;
handler()
{
foo = 1;
}
mainline()
{
del_timer_async(&timer);
foo = 2;
}
That is a race. So why do you say del_timer_sync() is not needed for
static timers?
>
> Of course. I repeat again and again, TCP use _reference_ _counting_.
Bear with me Alexey, I'm Australian. Where are the refcounts held?
Let's look at igmp.c:
static __inline__ void igmp_stop_timer(struct ip_mc_list *im)
{
// igmp_timer_expire() could be running right now
spin_lock_bh(&im->lock);
// and now
if (del_timer(&im->timer))
atomic_dec(&im->refcnt);
im->tm_running=0;
im->reporter = 0;
// and now.
im->unsolicit_count = 0;
spin_unlock_bh(&im->lock);
}
static void igmp_timer_expire(unsigned long data)
{
...
// Race here.
im->reporter = 1;
ip_ma_put(im);
}
I assume there is SOMETHING at a higher layer which prevents this
occurring. But what?